Radiopharmaceuticals, radioimaging agents, and uses thereof

ABSTRACT

The present invention relates to compounds that are useful as radiopharmaceuticals and radioimaging agents which bear a radionuclide-chelating agent. These coordinated compounds are useful in radiotherapy and diagnostic imaging. The invention also relates to methods of diagnosis, prognosis and therapy utilising the non-coordinated and radiolabelled compounds of the invention.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/198,131, filed Mar. 10, 2021, now allowed, which is a continuation ofU.S. patent application Ser. No. 16/619,073, filed Dec. 3, 2019, nowissued as U.S. Pat. No. 10,975,089, issued Apr. 13, 2021, which is anational stage application under 35 U.S.C. § 371 of InternationalApplication No. PCT/AU2018/050555, filed internationally on 5 Jun. 2018which claims Benefit of Australian Application No. 2017902151, filed on6 Jun. 2017, the contents of which are incorporated herein by referencein their entirety.

FIELD

The present invention relates to compounds that are useful asradiopharmaceuticals and radioimaging agents which bear aradionuclide-chelating agent. These coordinated compounds are useful inradiotherapy and diagnostic imaging. The invention also relates tomethods of diagnosis, prognosis and therapy utilising thenon-coordinated and radiolabelled compounds of the invention.

BACKGROUND

Prostate cancer is a leading cause of cancer-related deaths in men, withthe mortality rate often attributed to difficulties in the detection andsubsequent treatment of the disease. Prostate-related tumours often showincreased expression of prostate-specific membrane antigen (PSMA), whichis an enzyme typically expressed in prostate tissue but is oftenupregulated in some prostate cancers. This means that PSMA is a goodbiomarker or target for imaging, diagnostic, prognostic purposes.However since PSMA is also expressed in other tissues, both normal andmalignant, difficulties exist in successfully imaging prostate cancer.

Radiolabelled compounds may be used as a radiopharmaceutical orradioimaging agent, if the compound can bind sufficiently to the desiredsite and also deliver a radionuclide to the same site for the purposesof imaging or therapy.

Compounds or ligands containing a urea-based motif, such as theglutamate-substituted urea below are known to bind to the catalytic siteof PSMA with good affinity.

While compounds bearing this or similar motifs have been synthesised,problems relating to their stability or binding behaviour in vivo havebeen observed. For a compound to be useful in radioimaging orradiotherapy, the compound and the resultant complex comprising aradionuclide needs to be stable in vivo. One of the known problemsassociated with radiolabelled compounds is that the complex formed withthe radionuclide is not sufficiently strong and the radionuclide “leaks”out of the complex and is not delivered to the intended site. Furtherproblems that result from leakage of the radionuclides include thediffusion of the radionuclide to unwanted sites. This may lead tohealthy tissue being damaged as a result of the activity of theradionuclide. Furthermore, the diffusion of the radionuclide leads toimages of poorer quality, as the contrast between true binding sites(indicating the location of tumours) and sites with unwantedradionuclide is reduced.

Other problems associated with radiolabelled compounds include thepossibility of radiolysis, where the radioisotope itself leads to thedestruction of the compound and subsequent diffusion of theradionuclide. Radiolysis occurs as a result of the spontaneous decay ofradionuclide, with the energy released leading to the cleavage of bondsin the ligand and destruction of the complex. Radiolysis also leads tothe diffusion of the radionuclide to unwanted sites, which furthercontributes to the problems described above.

As the compound is to be administered to those in need, the compoundsmust also be inherently non-toxic to the subject. Another problemassociated with the use of radiolabelled compounds for diagnosis,imaging and therapy is the issue of binding affinity. Where the bindingaffinity for the target, i.e. PSMA in this instance, is low, the complexmay not achieve binding and be excreted, or may only show limitedbinding. Where the complex is immediately excreted, this leads to areduction in overall efficacy. However where the compound shows limitedexcretion and limited binding, the complex may diffuse throughout thesubject and lead to the unwanted effects described above. Furthermore,limited binding of the complex will likely reduce the time available foracceptable imaging or treatment of the tumour.

There exists a need for compounds that can provide the desired bindingaffinity to prostate cancer-related tumours and also have the ability toprovide the requisite imaging properties. There is also a requirementthat the compounds are sufficiently stable and do not undergodecomposition during use.

SUMMARY OF THE INVENTION

The present invention relates to novel compounds that show improvedbinding affinity to PSMA. The present inventors have found that the useof an amino acid-substituted urea bound to a macrocyclic sarcophaginevia specific linkers provides compounds that bind to PSMA and whencomplexed with a radionuclide, provide good/improved imaging properties.

In one aspect, the present invention provides a compound of Formula (I),or a salt, complex, isomer, solvate or prodrug thereof:

wherein:X is a group selected from H, OH, halogen, cyano, NO₂, NH₂, optionallysubstituted C₁-C₁₂ alkyl, optionally substituted amino, optionallysubstituted amide and optionally substituted aryl;Y is an optionally substituted C₁-C₁₂ alkylene group, wherein one ormore of the methylene groups in the alkylene group may be furtheroptionally substituted for a group selected from amido, carbonyl, ureaand thiourea;m is 0, 1, or 2; andn is 0, 1, or 2.

In an embodiment, the compound, or a salt, complex, isomer, solvate orprodrug thereof, has the formula:

In another embodiment, the compound, or a salt, complex, isomer, solvateor prodrug thereof, has the formula:

In another embodiment, the compound, or a salt, complex, isomer, solvateor prodrug thereof, has the formula:

In another aspect, the present invention provides a compositioncomprising a compound according to an aforementioned aspect, and apharmaceutically acceptable excipient.

In another aspect, the present invention provides an aqueous compositionfor parenteral administration comprising a compound of an aforementionedaspect; and wherein the composition further comprising ethanol, gentisicacid or a salt thereof, and sodium chloride.

In another aspect, the present invention provides a method for thetreatment or prevention of a condition in a subject in need thereof, themethod comprising administering a therapeutically effective amount of acompound according to an aforementioned aspect or a compositionaccording to an aforementioned aspect.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: PET imaging of LNCaPs bearing NSG mice treated with⁶⁴Cu-Sar-PSMA at 30 minutes, 2 hours and 22 hours.

FIG. 2: Graph showing biodistribution of ⁶⁴Cu-Sar-PSMA in LNCaPs bearingNSG mice (left), relative to levels in blood (right), both at 22 hours.

FIG. 3: PET imaging of LNCaPs bearing NSG mice treated with⁶⁴Cu-Sar-PSMA at 1 and 6 hours.

FIG. 4: Graph showing biodistribution of ⁶⁴Cu-Sar-PSMA in LNCaPs bearingNSG mice at 1 and 6 hours.

FIG. 5: Graph showing biodistribution of various radiolabelled complexesin LNCaPs xenograft mice, expressed as a ratio of uptake in tumor:kidneyat 1 hour.

FIG. 6: Graph showing preclinical biodistribution of ⁶⁴Cu-Sar-PSMA and⁶⁸Ga-labelled complexes in LNCaPs xenograft mice, expressed as a ratioof uptake in tumor:kidney at 1 hour.

FIG. 7: Graph showing biodistribution of various radiolabelled complexesin LNCaPs xenograft mice, expressed as a ratio of uptake intumor:kidney.

FIG. 8: Structures of PSMA ligand targets of the prior art.

FIG. 9: HPLC chromatogram of ⁶⁴Cu-Sar-PSMA (R_(T): 12.43 min) comparedto ^(nat)Cu-Sar-PSMA (R_(T): 12.38 min) with UV detection at 220 nm.

FIG. 10: Radio-HPLC chromatogram of ⁶⁴Cu-CoSar(PSMA)₂ (R_(T): 13.9 min).

FIG. 11: Analytical HPLC chromatogram of CoSar(PSMA)₂ (R_(T): 10.3 min)with UV detection at 220 nm.

DETAILED DESCRIPTION

As described and shown herein, the present inventors have found that acompound comprising an amino acid substituted-urea joined to asarcophagine cage via a linker group can bind to PSMA. Without wishingto be bound by theory, it is thought that the combination of the aminoacid-urea fragment, the linker and the sarcophagine cage provides theadvantages observed and discussed below.

The complexes as described herein are radiolabelled with a radionuclideor radioisotope that undergoes spontaneous decay, where these byproductsof decay are detected by various means, such as positron emissiontomography (PET) or single-photon emission computed tomography (SPECT).The quality of the images obtained, and subsequently the confidence inany diagnosis based on these images, depend on the ability of theradiolabelled complex to specifically bind to the prostate cancer site.

As used herein, the term “sarcophagine” refers to thenitrogen-containing macrocyclic ligand with the formula3,6,10,13,16,19-hexaazabicyclo[6.6.0]icosane.

The term “optionally substituted” as used throughout the specificationdenotes that the group may or may not be further substituted or fused(so as to form a condensed polycyclic system), with one or morenon-hydrogen substituent groups. In certain embodiments the substituentgroups are one or more groups independently selected from the groupconsisting of halogen, ═O, ═S, —CN, —NO₂, —CF₃, —OCF₃, alkyl, alkenyl,alkynyl, haloalkyl, haloalkenyl, haloalkynyl, heteroalkyl, cycloalkyl,cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, heteroaryl,cycloalkylalkyl, heterocycloalkylalkyl, heteroarylalkyl, arylalkyl,cycloalkylalkenyl, heterocycloalkylalkenyl, arylalkenyl,heteroarylalkenyl, cycloalkylheteroalkyl, heterocycloalkyl heteroalkyl,arylheteroalkyl, heteroarylheteroalkyl, hydroxy, hydroxyalkyl, alkyloxy,alkyloxyalkyl, alkyloxycycloalkyl, alkyloxyheterocycloalkyl,alkyloxyaryl, alkyloxyheteroaryl, alkyloxycarbonyl, alkylaminocarbonyl,alkenyloxy, alkynyloxy, cycloalkyloxy, cycloalkenyloxy,heterocycloalkyloxy, heterocycloalkenyloxy, aryloxy, phenoxy, benzyloxy,heteroaryloxy, arylalkyloxy, amino, alkylamino, acylamino, aminoalkyl,arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl,arylsulfonyl, aminosulfonyl, sulfinyl, alkylsulfinyl, arylsulfinyl,aminosulfinylaminoalkyl, —C(═O)OH, —C(═O)R^(a), —C(═O)OR^(a),C(═O)NR^(a)R^(b), C(═NOH)R^(a), C(═NR^(a))NR^(b)R^(c), NR^(a)R^(b),NR^(a)C(═O)R^(b), NR^(a)C(═O)OR^(b), NR^(a)C(═O)NR^(b)R^(c),NR^(a)C(═NR^(b))NR^(c)R^(d), NR^(a)SO₂R^(b), —SR^(a), SO₂NR^(a)R^(b),—OR^(a), OC(═O)NR^(a)R^(b), OC(═O)R^(a) and acyl, wherein R^(a), R^(b),R^(c) and R^(d) are each independently selected from the groupconsisting of H, C₁-C₁₂alkyl, C₁-C₁₂haloalkyl, C₂-C₁₂alkenyl,C₂-C₁₂alkynyl, C₂-C₁₀ heteroalkyl, C₃-C₁₂cycloalkyl, C₃-C₁₂cycloalkenyl,C₂-C₁₂heterocycloalkyl, C₂-C₁₂ heterocycloalkenyl, C₆-C₁₈aryl,C₁-C₁₈heteroaryl, and acyl, or any two or more of R^(a), R^(b), R^(c)and R^(d), when taken together with the atoms to which they are attachedform a heterocyclic ring system with 3 to 12 ring atoms.

In some embodiments, each optional substituent is independently selectedfrom the group consisting of: halogen, ═O, ═S, —CN, —NO₂, —CF₃, —OCF₃,alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl,heteroalkyl, cycloalkyl, cycloalkenyl, heterocycloalkyl,heterocycloalkenyl, aryl, heteroaryl, hydroxy, hydroxyalkyl, alkyloxy,alkyloxyalkyl, alkyloxyaryl, alkyloxyheteroaryl, alkenyloxy, alkynyloxy,cycloalkyloxy, cycloalkenyloxy, heterocycloalkyloxy,heterocycloalkenyloxy, aryloxy, heteroaryloxy, arylalkyl,heteroarylalkyl, arylalkyloxy, amino, alkylamino, acylamino, aminoalkyl,arylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl,aminoalkyl, —COOH, —SH, and acyl.

Examples of particularly suitable optional substituents include F, Cl,Br, I, CH₃, CH₂CH₃, OH, OCH₃, CF₃, OCF₃, NO₂, NH₂, COOH, COOCH₃ and CN.

“Alkenyl” as a group or part of a group denotes an aliphatic hydrocarbongroup containing at least one carbon-carbon double bond and which may bestraight or branched preferably having 2-12 carbon atoms, morepreferably 2-10 carbon atoms, most preferably 2-6 carbon atoms, in thenormal chain. The group may contain a plurality of double bonds in thenormal chain and the orientation about each is independently E or Z.Exemplary alkenyl groups include, but are not limited to, ethenyl,propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl and nonenyl.

“Alkyl” as a group or part of a group refers to a straight or branchedaliphatic hydrocarbon group, preferably a C₁-C₁₂ alkyl, more preferablya C₁-C₁₀ alkyl, most preferably C₁-C₆ unless otherwise noted. Examplesof suitable straight and branched C₁-C₆ alkyl substituents includemethyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, t-butyl, hexyl,and the like.

“Alkynyl” as a group or part of a group means an aliphatic hydrocarbongroup containing a carbon-carbon triple bond and which may be straightor branched preferably having from 2-12 carbon atoms, more preferably2-10 carbon atoms, more preferably 2-6 carbon atoms in the normal chain.Exemplary structures include, but are not limited to, ethynyl andpropynyl.

“Aryl” as a group or part of a group denotes (i) an optionallysubstituted monocyclic, or fused polycyclic, aromatic carbocycle (ringstructure having ring atoms that are all carbon) preferably having from5 to 12 atoms per ring. Examples of aryl groups include phenyl,naphthyl, and the like; (ii) an optionally substituted partiallysaturated bicyclic aromatic carbocyclic moiety in which a phenyl and aC₅₋₇ cycloalkyl or C₅₋₇ cycloalkenyl group are fused together to form acyclic structure, such as tetrahydronaphthyl, indenyl or indanyl.Typically an aryl group is a C₆-C₁₈ aryl group.

“Cycloalkyl” refers to a saturated monocyclic or fused or spiropolycyclic, carbocycle preferably containing from 3 to 9 carbons perring, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and thelike, unless otherwise specified. It includes monocyclic systems such ascyclopropyl and cyclohexyl, bicyclic systems such as decalin, andpolycyclic systems such as adamantane. A cycloalkyl group typically is aC₃-C₉ cycloalkyl group.

“Halogen” represents chlorine, fluorine, bromine or iodine.

“Heteroalkyl” refers to a straight- or branched-chain alkyl grouppreferably having from 2 to 12 carbons, more preferably 2 to 6 carbonsin the chain, in which one or more of the carbon atoms (and anyassociated hydrogen atoms) are each independently replaced by aheteroatomic group selected from S, O, P and NR′ where R′ is selectedfrom the group consisting of H, optionally substituted C₁-C₁₂alkyl,optionally substituted C₃-C₁₂cycloalkyl, optionally substitutedC₆-C₁₈aryl, and optionally substituted C₁-C₁₈heteroaryl. Exemplaryheteroalkyls include alkyl ethers, secondary and tertiary alkyl amines,amides, alkyl sulfides, and the like. Examples of heteroalkyl alsoinclude hydroxyC₁-C₆alkyl, C₁-C₆alkyloxyC₁-C₆alkyl, aminoC₁-C₆alkyl,C₁-C₆alkylaminoC₁-C₆alkyl, and di(C₁-C₆alkyl)aminoC₁-C₆alkyl

“Heteroaryl” either alone or part of a group refers to groups containingan aromatic ring (preferably a 5 or 6 membered aromatic ring) having oneor more heteroatoms as ring atoms in the aromatic ring with theremainder of the ring atoms being carbon atoms. Suitable heteroatomsinclude nitrogen, oxygen and sulphur. Examples of heteroaryl includethiophene, benzothiophene, benzofuran, benzimidazole, benzoxazole,benzothiazole, benzisothiazole, naphtho[2,3-b]thiophene, furan,isoindolizine, xantholene, phenoxatine, pyrrole, imidazole, pyrazole,pyridine, pyrazine, pyrimidine, pyridazine, tetrazole, indole,isoindole, 1H-indazole, purine, quinoline, isoquinoline, phthalazine,naphthyridine, quinoxaline, cinnoline, carbazole, phenanthridine,acridine, phenazine, thiazole, isothiazole, phenothiazine, oxazole,isooxazole, furazane, phenoxazine, 2-, 3- or 4-pyridyl, 2-, 3-, 4-, 5-,or 8-quinolyl, 1-, 3-, 4-, or 5-isoquinolinyl, 1-, 2-, or 3-indolyl, and2-, or 3-thienyl. A heteroaryl group is typically a C₁-C₁₈ heteroarylgroup.

As used herein, the term “C₁-C₁₂ alkylene” refers to a bivalent straightor branched chain aliphatic hydrocarbon group, where the group has 1 to12 carbon atoms in the chain.

In an embodiment, X is an optionally substituted C₁-C₁₂ alkyl.

In an embodiment, X is C₁-C₁₂ alkyl.

In an embodiment, X is an optionally substituted C₁-C₃ alkyl.

In an embodiment, X is C₁-C₃ alkyl.

In an embodiment, X is methyl.

In an embodiment, X is CH₃.

In an embodiment, X is an optionally substituted amino, for example—NCH₃.

In an embodiment, X is amino.

In an embodiment, X is an optionally substituted amide. As used herein,the term “amide” refers to a functional group consisting of a carbonylgroup attached to a nitrogen atom. Therefore, the term “optionallysubstituted amide” refers to an amide functional group that bearsfurther substitution.

In an embodiment, X is an optionally substituted amide, for example,

In an embodiment, Y is a substituted alkylene group.

In an embodiment, Y is an unsubstituted alkylene group.

In an embodiment, Y is CH₂.

In an embodiment, Y is a carbonyl group.

In an embodiment, Y is a substituted C₁-C₁₂ alkylene group, wherein oneor more of the methylene groups is further substituted with an amidogroup, for example,

In an embodiment, n is 1.

In an embodiment, n is 2.

In an embodiment, n is 0.

In an embodiment, m is 1.

In an embodiment, m is 2.

In an embodiment, m is 0.

In an embodiment, the present invention provides a compound of formula:

In another embodiment, the present invention provides a compound offormula:

where the two phenylalanine residues are D-Phe, to give aMeCOSar-D-Phe-D-Phe-AOC-Lys-urea-Glu ligand. The inventors haveidentified that the use of phenylalanine residues with specificallyD-stereochemistry may give rise to compounds with improved metabolicstability. Additionally, the inventors have also identified that the useof two D-Phe residues in the ligand may increase the hydrophobicity ofthe compounds and potential pi-pi interactions of the ligand with thebinding pocket of the target enzyme.

In another embodiment, the present invention provides a compound offormula

In another embodiment, the present invention provides a compound offormula:

This compound comprises two linkers and two urea motifs for binding toPSMA. Without wishing to be bound by theory, it would appear that thiscompound bearing two urea motifs may show further improved bindingaffinity to PSMA. It is also thought that this bis derivative, i.e.compound with two linkers and two urea motifs, may provide a bettersignal to noise ratio when used for imaging purposes and as compared tothe corresponding mono compound with a single linker and urea motif. Thebis compound may also show a further improvement in clearance from thekidneys when administered. This may be attributed to the difference inoverall charge and charge separation and distribution, when the mono andbis compounds are compared.

In another embodiment, the present invention provides a compound offormula:

In another embodiment, the present invention provides a compound offormula:

In another embodiment, the present invention provides a compound offormula:

In an embodiment, the compound is coordinated with a metal ion.

In an embodiment, the metal ion is an ion of Cu, Tc, Gd, Ga, In, Co, Re,Fe, Au, Mg, Ca, Ag, Rh, Pt, Bi, Cr, W, Ni, V, Ir, Zn, Cd, Mn, Ru, Pd,Hg, Ti, Lu, Sc, Zr, Pb, Ac and Y.

In an embodiment, the metal ion is a radionuclide.

In some embodiments, the metal in the metal ion is a radionuclideselected from the group consisting of Cu, Tc, Ga, Co, In, Fe, and Ti.The present compounds have been found to be particularly applicableuseful in binding copper ions. In some embodiments the metal in themetal ion is a radionuclide selected from the group consisting of ⁶⁰Cu,⁶¹Cu, ⁶²Cu, ⁶⁴Cu and ⁶⁷Cu. In some embodiments the metal in the metalion is ⁶⁰Cu. In some embodiments the metal in the metal ion is ⁶¹Cu. Insome embodiments the metal in the metal ion is ⁶²Cu. In some embodimentsthe metal in the metal ion is ⁶⁴Cu. In some embodiments the metal in themetal ion is ⁶⁷Cu.

The compound of Formula (I) comprises a sarcophagine macrocyclic ligandand a Lys-urea-Glu moiety that targets PSMA. The compound also comprisesintervening parts that link the sarcophagine and PSMA-targeting moiety.In Formula (I), these include a propyl linker bound by two amide groups,two phenylalanine residues and an aminooctanoic acid (AOC) group. Thepropyl linker, phenylalanine residues and aminooctanoic acid grouptogether act as a spacer group to separate the sarcophagine andPSMA-targeting moiety. It is desirable that there is a degree ofseparation between the sarcophagine and the PSMA-targeting moiety, so asto ensure that the activity of these two groups do not interfere witheach other, however it is also important that these two groups are notso far apart, such that where the sarcophagine contains a boundradionuclide, the radionuclide complex is delivered to the site ofaction identified by the PSMA-targeting moiety. The PSMA targetingmoiety comprises a Lys-urea-Glu moiety, which has three carboxyfunctional groups that provide an overall negative charge and contributeto a zinc binding region. The aminooctanoic acid group adjacent to thePSMA targeting moiety is designed to provide a linker group ofapproximately 20 Å in length in order to separate the charge between thePSMA targeting moiety and the remainder of the molecule. The twoD-phenylalanine residues are hydrophobic in nature and allow for pi-pibinding interactions with the active site. These residues alsocontribute to the metabolic stability of the compound. The propylenegroup situated between two amide functional groups also serve to providethe requisite distance between the macrocyclic ligand (which chelates apositively charged Cu ion) and the PSMA targeting moiety. The presentinventors have found that the compounds according to the presentinvention comprise various fragments (i.e. macrocyclic ligand, linkersand PSMA targeting moiety), which together provide a PSMA-binding ligandwith the requisite stability and binding affinity.

In an embodiment, the invention provides compositions comprising acompound as described above together with a pharmaceutically acceptableexcipient.

In a further aspect, the invention provides a method of treating orpreventing a condition in a subject in need thereof, the methodcomprising administering a therapeutically effective amount of acompound as described above or a composition thereof.

In an embodiment, the condition is cancer.

In an embodiment, the condition is breast cancer, colon cancer, lungcancer, ovarian cancer, prostate cancer, head and/or neck cancer, orrenal, gastric, pancreatic cancer, brain cancer a hematologic malignancysuch as lymphoma or leukaemia

In an embodiment, the condition is prostate cancer.

In a further aspect the invention provides a method of radioimaging asubject, the method comprising administering an effective amount of acompound as described above or a composition thereof.

Ideally, a radiopharmaceutical is retained at the intended target andnot at any other sites, and any unbound radiopharmaceutical cleared fromthe circulatory system. This would then allow for images with sufficientcontrast to be obtained, which then in turn allows for a more accurateanalysis and diagnosis to be performed. For this to occur, theradiolabelled complex should have physical and chemical properties wherethe bound complex remains bound at the desired site for a timesufficient for the requisite imaging, however any unbound complex shouldbe cleared sufficiently from the subject to prevent any backgroundradiation arising from the unbound complex to interfere and reduce thecontrast of the images obtained.

The compounds of the present invention show a more favourabledistribution profile in vivo. FIGS. 2 and 4 show that the administrationof ⁶⁴Cu-Sar-PSMA to tumour-bearing mice leads to the localisation of thecompound in the tumour, rather than in any major organs or blood.Minimising binding of the radiolabelled complex to other tissues reducesthe damage to healthy tissue. The complex shows relatively littleaccumulation in the bloodstream, which also shows the high bindingaffinity of the Sar-PSMA complex to tumours that express PSMA.

In comparison with other known radiolabelled complexes (see FIG. 5),such as ⁶⁸Ga-PSMA-617, ¹⁷⁷Lu-PSMA-I&T and ⁶⁸Ga-DOTAGA-ffk(PSMA), the⁶⁴Cu-Sar-PSMA complex shows greater uptake in tumours. Additionally,when uptake into the kidneys is considered, which signifies excretion ofthe compound, ⁶⁴Cu-Sar-PSMA shows markedly less uptake into the kidneyswhen compared to other compounds that show similar binding to the tumoursite. A similar comparison between the ⁶⁴Cu-Sar-PSMA complex and various⁶⁸Ga complexes is shown in FIG. 6, which shows that the use of a ⁶⁴Curadionuclide binds to the tumour as well, or better than, the complexesthat use a ⁶⁸Ga radionuclide. Furthermore, the ⁶⁴Cu-Sar-PSMA complexshows less uptake into the kidneys than the complexes with a ⁶⁸Garadionuclide.

Subsequently, the present inventors have found that the use of theSar-PSMA ligand and a ⁶⁴Cu radionuclide shows better affinity for thetumour site and better clearance from the kidneys after administration.These advantages allow for better imaging results to be obtained, i.e.higher affinity for the tumour site provides images with bettercontrast, as the radionuclide is predominantly located at the targetsite and better removal of unbound ligand from the circulation, therebyreducing background accumulation. This then allows for improveddiagnosis of tumours such as prostate cancer. The increased affinity forthe tumour binding site also suggests that there is less diffusion ofthe radionuclide to other tissues, which improves the quality of theimages obtained. Furthermore, minimising the diffusion of theradionuclide to areas that are not the tumour site means that less ofthe radiolabelled complex is required for administration and that anydetrimental effects from the radioactive complex is localised, such thathealthy tissue is not affected.

The inventors have found that the present compounds may be used astheranostic compounds. The theranostic approach allows for the samecompound to be used in the diagnosis and treatment of an indication,which provides advantages over the use of one compound for diagnosis anda different compound for treatment. Overall, this allows for greaterefficiency in diagnosis and treatment of a particular disease. This isin contrast to traditional methods, where a ligand with a particularisotope may be suitable for diagnosing a disease, however the samecombination of ligand and isotope may not be suitable for treating thedisease. This then requires that the ligand, the isotope or both theligand and isotope are modified in order to treat the disease.

FIG. 7 shows the accumulation of radiolabelled complexes in tumours andthe kidney over time. Where the ⁶⁴Cu-Sar-PSMA complex is administered,the ratio of the complex located in the tumour to the complex located inthe tumour increases up to a time of 24 hours. FIG. 7 shows that theuptake of the ⁶⁴Cu-Sar-PSMA complex in tumour sites after 1 hour isgreater than the other radiolabelled complexes, which indicates that the⁶⁴Cu-Sar-PSMA complex is taken up faster than the other comparatorcomplexes. Furthermore, the ratio of the complex in tumours to thekidney increases up to a time of 24 hours, which then indicates that thecomplex has a favourable binding affinity to the tumour. The advantagesarising from this is that as the complex remains bound for a longerperiod of time, imaging of the subject can be performed over this timeperiod to allow for images of better quality and higher contrast can beobtained. This then allows for a more accurate diagnosis of the diseaseto be made.

The ⁶⁴Cu-Sar-PSMA complex shows improved binding affinity over otherradiolabelled complexes, which also indicates that the same complex maybe of use for therapy. As the therapeutic nature of the complex relieson the delivery of the radionuclide to the target site, i.e. the tumour,good specificity and affinity for the tumour site is necessary. Thisallows for the radionuclide to deliver the radiotherapeutic effect tothe desired site and prevent damage to other tissues. Furthermore, theability of the radiolabelled complex to remain bound to the target siteallows for a prolonged therapeutic effect to be delivered, whichincreases the efficiency of the method of treatment.

The present inventors have now shown that the ⁶⁴Cu-Sar-PSMAradiolabelled complex has sufficient binding specificity and affinityfor the target PSMA site, such that administration of a therapeuticallyeffective amount of the radiolabelled complex may allow for thetreatment of prostate cancer.

The present inventors have also now shown that the Sar-PSMA complexradiolabelled with a copper isotope may be used for both diagnostic andtherapeutic purposes. For example, the ⁶⁴Cu-Sar-PSMA radiolabelledcomplex may be used for both diagnostic and therapeutic purposes. The⁶⁷Cu-Sar-PSMA radiolabelled complex may also be used for both diagnosticand therapeutic purposes.

The term “pharmaceutically acceptable salts” refers to salts that retainthe desired biological activity of the above-identified compounds, andinclude pharmaceutically acceptable acid addition salts and baseaddition salts. Suitable pharmaceutically acceptable acid addition saltsof compounds of Formula (I) may be prepared from an inorganic acid orfrom an organic acid. Examples of such inorganic acids are hydrochloric,sulfuric, and phosphoric acid. Appropriate organic acids may be selectedfrom aliphatic, cycloaliphatic, aromatic, heterocyclic carboxylic andsulfonic classes of organic acids, examples of which are formic, acetic,propionic, succinic, glycolic, gluconic, lactic, malic, tartaric,citric, fumaric, maleic, alkyl sulfonic and arylsulfonic. Additionalinformation on pharmaceutically acceptable salts can be found inRemington's Pharmaceutical Sciences, 19th Edition, Mack Publishing Co.,Easton, Pa. 1995. In the case of agents that are solids, it isunderstood by those skilled in the art that the inventive compounds,agents and salts may exist in different crystalline or polymorphicforms, all of which are intended to be within the scope of the presentinvention and specified formulae.

The term “therapeutically effective amount” or “effective amount” is anamount sufficient to effect beneficial or desired clinical results. Aneffective amount can be administered in one or more administrations. Aneffective amount is typically sufficient to palliate, ameliorate,stabilize, reverse, slow or delay the progression of the disease state.An effective amount for radioimaging is typically sufficient to identifythe radionuclide in the subject.

The monitoring of the subject for the location of the radiolabelledmaterial will typically provide the analyst with information regardingthe location of the radiolabelled material and hence the location of anymaterial that is targeted by the molecular recognition moiety (such ascancerous tissue). An effective amount of the compounds of the inventionwill depend upon a number of factors and will of necessity involve abalance between the amount of radioactivity required to achieve thedesired radio imaging effect and the general interest in not exposingthe subject (or their tissues or organs) to any unnecessary levels ofradiation which may be harmful.

The methods of treatment of the present invention involve administrationof a compound of formula (I) which has been complexed to a radionuclide.The compounds of formula (I) are able to deliver the radionuclide to thedesired location in the body where its mode of action is desired.

A therapeutically effective amount can be readily determined by anattending clinician by the use of conventional techniques and byobserving results obtained under analogous circumstances. In determiningthe therapeutically effective amount a number of factors are to beconsidered including but not limited to, the species of animal, itssize, age and general health, the specific condition involved, theseverity of the condition, the response of the patient to treatment, theparticular radio labelled compound administered, the mode ofadministration, the bioavailability of the preparation administered, thedose regime selected, the use of other medications and other relevantcircumstances.

In addition the treatment regime will typically involve a number ofcycles of radiation treatment with the cycles being continued until suchtime as the condition has been ameliorated. Once again the optimalnumber of cycles and the spacing between each treatment cycle willdepend upon a number of factors such as the severity of the conditionbeing treated, the health (or lack thereof) of the subject being treatedand their reaction to radiotherapy. In general the optimal dosage amountand the optimal treatment regime can be readily determined by a skilledaddressee in the art using well known techniques.

In using the compounds of the invention they can be administered in anyform or mode which makes the compound available for the desiredapplication (imaging or radio therapy). One skilled in the art ofpreparing formulations of this type can readily select the proper formand mode of administration depending upon the particular characteristicsof the compound selected, the condition to be treated, the stage of thecondition to be treated and other relevant circumstances. We refer thereader to Remington's Pharmaceutical Sciences, 19th edition, MackPublishing Co. (1995) for further information.

The compounds of the present invention can be administered alone or inthe form of a pharmaceutical composition in combination with apharmaceutically acceptable carrier, diluent or excipient. The compoundsof the invention, while effective themselves, are typically formulatedand administered in the form of their pharmaceutically acceptable saltsas these forms are typically more stable, more easily crystallised andhave increased solubility.

The compounds are, however, typically used in the form of pharmaceuticalcompositions which are formulated depending on the desired mode ofadministration. The compositions are prepared in manners well known inthe art.

The invention in other embodiments provides a pharmaceutical pack or kitcomprising one or more containers filled with one or more of theingredients of the pharmaceutical compositions of the invention. In sucha pack or kit can be found at least one container having a unit dosageof the agent(s). Conveniently, in the kits, single dosages can beprovided in sterile vials so that the clinician can employ the vialsdirectly, where the vials will have the desired amount and concentrationof compound and radio nucleotide which may be admixed prior to use.Associated with such container(s) can be various written materials suchas instructions for use, or a notice in the form prescribed by agovernmental agency regulating the manufacture, use or sale ofpharmaceuticals, imaging agents or biological products, which noticereflects approval by the agency of manufacture, use or sale for humanadministration.

The compounds of the invention may be used or administered incombination with one or more additional drug(s) that are anti-cancerdrugs and/or procedures (e.g. surgery, radiotherapy) for the treatmentof the disorder/diseases mentioned. The components can be administeredin the same formulation or in separate formulations. If administered inseparate formulations the compounds of the invention may be administeredsequentially or simultaneously with the other drug(s).

In addition to being able to be administered in combination with one ormore additional drugs that include anti-cancer drugs, the compounds ofthe invention may be used in a combination therapy. When this is donethe compounds are typically administered in combination with each other.Thus one or more of the compounds of the invention may be administeredeither simultaneously (as a combined preparation) or sequentially inorder to achieve a desired effect. This is especially desirable wherethe therapeutic profile of each compound is different such that thecombined effect of the two drugs provides an improved therapeuticresult.

Pharmaceutical compositions of this invention for parenteral injectioncomprise pharmaceutically acceptable sterile aqueous or nonaqueoussolutions, dispersions, suspensions or emulsions as well as sterilepowders for reconstitution into sterile injectable solutions ordispersions just prior to use. Examples of suitable aqueous andnonaqueous carriers, diluents, solvents or vehicles include water,ethanol, polyols (such as glycerol, propylene glycol, polyethyleneglycol, and the like), and suitable mixtures thereof, vegetable oils(such as olive oil), and injectable organic esters such as ethyl oleate.Proper fluidity can be maintained, for example, by the use of coatingmaterials such as lecithin, by the maintenance of the required particlesize in the case of dispersions, and by the use of surfactants.

These compositions may also contain adjuvants such as preservative,wetting agents, emulsifying agents, and dispersing agents. Prevention ofthe action of micro-organisms may be ensured by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents such as sugars, sodium chloride,and the like. Prolonged absorption of the injectable pharmaceutical formmay be brought about by the inclusion of agents that delay absorptionsuch as aluminium monostearate and gelatin.

If desired, and for more effective distribution, the compounds can beincorporated into slow release or targeted delivery systems such aspolymer matrices, liposomes, and microspheres.

The injectable formulations can be sterilized, for example, byfiltration through a bacterial-retaining filter, or by incorporatingsterilizing agents in the form of sterile solid compositions that can bedissolved or dispersed in sterile water or other sterile injectablemedium just prior to use.

In an embodiment, the present invention provides an aqueous compositionof a compound of Formula (I) or a salt thereof:

wherein:X is a group selected from H, OH, halogen, cyano, NO₂, NH₂, optionallysubstituted C₁-C₁₂ alkyl, optionally substituted amino, optionallysubstituted amide and optionally substituted aryl;Y is an optionally substituted C₁-C₁₂ alkylene group, wherein one ormore of the methylene groups in the alkylene groups is optionallysubstituted for a group selected from amide, carbonyl, urea andthiourea;m is 0, 1, or 2; andn is 0, 1, or 2;wherein the compound of Formula (I) is complexed with a Cu ion;and wherein the composition further comprising ethanol, gentisic acid ora salt thereof, and sodium chloride.

The present inventors have identified that the use of gentisic acid andethanol in a composition of the compound of Formula (I) with acomplexing Cu ion may assist in preventing or minimising radiolysis ofthe radiolabelled complex.

In the above embodiments, the compositions of the present inventioncomprise ethanol as a component. The ethanol used in the composition maybe anhydrous ethanol. Alternatively, the ethanol used in the compositionmay not have been subject to drying processes and may be hydrated. Theethanol is preferably pharmaceutical grade ethanol. The ethanol presentin the composition may assist in preventing radiolysis of theradiolabelled complex of Formula (I).

In the above embodiments, the compositions of the present invention alsocomprise sodium chloride as a component. The sodium chloride in theformulations of the present invention may be provided as a salinesolution. A saline solution is defined as an aqueous solution of sodiumchloride. For example, normal saline is defined as an aqueous solutionof sodium chloride at a concentration of 0.9% (w/v). In an embodiment ofthe present invention, the sodium chloride of a formulation is providedby a saline solution.

In the above embodiments, the compositions of the present inventioncomprise gentisic acid, or pharmaceutically acceptable salts and/orhydrates thereof, as a component. Gentisic acid is also known as2,5-dihydroxybenzoic acid, 5-hydroxysalicylic acid orhydroquinonecarboxylic acid. Salts of gentisic acid may include thesodium salt and the sodium salt hydrate. Any reference to gentisic acidmay include a reference to salts thereof, where relevant. It has beenidentified by the present inventors that the gentisic acid, or saltthereof, within the present composition may assist in preventing orminimising radiolysis of the radiolabelled complex of Formula (I).

Solid dosage forms for oral administration include capsules, tablets,pills, powders, and granules. In such solid dosage forms, the activecompound is mixed with at least one inert, pharmaceutically acceptableexcipient or carrier such as sodium citrate or dicalcium phosphateand/or a) fillers or extenders such as starches, lactose, sucrose,glucose, mannitol, and silicic acid, b) binders such as, for example,carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone,sucrose, and acacia, c) humectants such as glycerol, d) disintegratingagents such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates, and sodium carbonate, e) solutionretarding agents such as paraffin, f) absorption accelerators such asquaternary ammonium compounds, g) wetting agents such as, for example,cetyl alcohol and glycerol monostearate, h) absorbents such as kaolinand bentonite clay, and i) lubricants such as talc, calcium stearate,magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate,and mixtures thereof. In the case of capsules, tablets and pills, thedosage form may also comprise buffering agents.

Solid compositions of a similar type may also be employed as fillers insoft and hard-filled gelatin capsules using such excipients as lactoseor milk sugar as well as high molecular weight polyethylene glycols andthe like.

The solid dosage forms of tablets, dragees, capsules, pills, andgranules can be prepared with coatings and shells such as entericcoatings and other coatings well known in the pharmaceutical formulatingart. They may optionally contain opacifying agents and can also be of acomposition that they release the active ingredient(s) only, orpreferentially, in a certain part of the intestinal tract, optionally,in a delayed manner. Examples of embedding compositions which can beused include polymeric substances and waxes.

If desired, and for more effective distribution, the compounds can beincorporated into slow release or targeted delivery systems such aspolymer matrices, liposomes, and microspheres.

The active compounds can also be in microencapsulated form, ifappropriate, with one or more of the above-mentioned excipients.

Liquid dosage forms for oral administration include pharmaceuticallyacceptable emulsions, solutions, suspensions, syrups and elixirs. Inaddition to the active compounds, the liquid dosage forms may containinert diluents commonly used in the art such as, for example, water orother solvents, solubilizing agents and emulsifiers such as ethylalcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzylalcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol,dimethyl formamide, oils (in particular, cottonseed, groundnut, corn,germ, olive, castor, and sesame oils), glycerol, tetrahydrofurfurylalcohol, polyethylene glycols and fatty acid esters of sorbitan, andmixtures thereof.

Besides inert diluents, the oral compositions can also include adjuvantssuch as wetting agents, emulsifying and suspending agents, sweetening,flavoring, and perfuming agents.

Suspensions, in addition to the active compounds, may contain suspendingagents as, for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminiummetahydroxide, bentonite, agar-agar, and tragacanth, and mixturesthereof.

As discussed above, the compounds of the embodiments may be useful fortreating and/or detecting proliferative diseases. Examples of such cellproliferative diseases or conditions include cancer (include anymetastases), psoriasis, and smooth muscle cell proliferative disorderssuch as restenosis. The compounds of the present invention may beparticularly useful for treating and/or detecting tumours such as breastcancer, colon cancer, lung cancer, ovarian cancer, prostate cancer, headand/or neck cancer, or renal, gastric, pancreatic cancer and braincancer as well as hematologic malignancies such as lymphoma andleukaemia. In addition, the compounds of the present invention may beuseful for treating and/or detecting a proliferative disease that isrefractory to the treatment and/or detecting with other anti-cancerdrugs; and for treating and/or detecting hyperproliferative conditionssuch as leukaemia's, psoriasis and restenosis. In other embodiments,compounds of this invention can be used to treat and/or detectpre-cancer conditions or hyperplasia including familial adenomatouspolyposis, colonic adenomatous polyps, myeloid dysplasia, endometrialdysplasia, endometrial hyperplasia with atypia, cervical dysplasia,vaginal intraepithelial neoplasia, benign prostatic hyperplasia,papillomas of the larynx, actinic and solar keratosis, seborrheickeratosis and keratoacanthoma.

Synthesis of Compounds of the Invention

The agents of the various embodiments may be prepared using the reactionroutes and synthesis schemes as described below, employing thetechniques available in the art using starting materials that arereadily available. The preparation of particular compounds of theembodiments is described in detail in the following examples, but theartisan will recognize that the chemical reactions described may bereadily adapted to prepare a number of other agents of the variousembodiments. For example, the synthesis of non-exemplified compounds maybe successfully performed by modifications apparent to those skilled inthe art, e.g. by appropriately protecting interfering groups, bychanging to other suitable reagents known in the art, or by makingroutine modifications of reaction conditions. A list of suitableprotecting groups in organic synthesis can be found in T. W. Greene'sProtective Groups in Organic Synthesis, 3^(rd) Edition, John Wiley &Sons, 1991. Alternatively, other reactions disclosed herein or known inthe art will be recognized as having applicability for preparing othercompounds of the various embodiments. Reagents useful for synthesizingcompounds may be obtained or prepared according to techniques known inthe art.

Example 1 Synthesis of Sar-PSMA

Scheme 1 outlines the route taken for the synthesis of the compound ofSar-PSMA 1.

The MeCOSar-D-Phe-D-Phe-Aoc-Lys-urea-Glu ligand 1, whereAoc=8-aminooctanoic acid (i.e. Sar-PSMA), was prepared via solid phasepeptide synthesis. The glutamate-urea-lysine binding motif wassynthesized by reacting an imidazole-activated and protected glutamicacid with protected L-lysine that had been immobilised on Wang resin.The peptide linker was conjugated to the ε-amine of lysine viasolid-phase peptide synthesis using a standard Fmoc protocol. Theconjugation of the chelator was performed by reacting (tBoc)₄₋₅MeCOSarwith the side-chain protected linker-urea on solid support. The Sar-PSMAwas cleaved from the resin and deprotected simultaneously(TFA/TIPS/H₂O).

Radiolabelling of Sar-PSMA with ⁶⁴Cu^(II)

The Sar-PSMA ligand 1 was radiolabelled with ⁶⁴Cu^(II) at roomtemperature in aqueous solution (0.1 M NH₄OAc, pH 8, 1-10 nmolSar-PSMA). Elution from a solid-phase cartridge (Phenomenex Strata-X RP60 mg/mL) afforded ⁶⁴Cu-Sar-PSMA in >94% yield (n.d.c.) and >97%radiochemical yield (7.95-21.9 GBq/μmol).

Synthesis of Activated Glu Intermediate, 3

Reference: Duspara, P. A.; Islam, M. S.; Lough, A. 3.; Batey, R. A.,Synthesis and reactivity of N-alkyl carbamoylimidazoles: development ofN-methyl carbamoylimidazole as a methyl isocyanate equivalent. J OrgChem 2012, 77 (22), 10362-8.

To a flask containing L-Bis(tBu)Glu HCl 2 (3.56 g, 12.04 mmol, 1.0 eq)and carbonyl diimidazole (2.15 g, 13.24 mmol, 1.1 eq) was added a 1:5mixture of DMF/MeCN (50 mL). The reaction was stirred overnight at RT.After stirring, the solvent was removed in vacuo and the remaining crudemixture was dissolved and purified via flash chromatography (mobilephase: 7:3:1 petroleum spirits/chloroform/methanol, R_(f): ˜0.24, 30:1silica/crude mass ratio) to afford the product as a whitesemi-crystalline powder, (2.25 g, 52.9% yield).

Loading of Wang Resin with Fmoc-Lys(DDiv)-OH

To a 50 mL falcon tube containing Wang Resin (1.028 g, 1.15 mmol/g, 1.18mmol) was added a preactivated mixture of Fmoc-Lys(DDiv)-OH (2.038 g,3.55 mmol, 3.0 eq), HCTU (1.33 g, 3.5 mmol, 2.96 eq), DIPEA (1.24 mL,7.09 mmol, 6 eq), DMAP (43.3 mg, 0.355 mmol, 0.3 eq) in DMF. The resinwas placed on the shaker for 2 h and allowed to react. To the reactionmixture was then added acetic anhydride (223 μL, 2.36 mmol, 2 eq) andpyridine (190 μL, 2.36 mmol, 2 eq) to cap the remaining functionalgroups of resin and stirred for 30 min. The resin was then filtered andwashed with DMF ×3, DCM ×3, MeOH ×2, and Et₂O ×2, dried, and weighed todetermine the final resin loading (0.759 mmol/g). Resin loading wasdetermined as follows:

${{Resin}{Loading}} = {\frac{{{final}{weight}} - {{initial}{weight}}}{MW{of}{Fmoc} - {{Lys}({DDiv})} - {OH}}{mmol}/g}$

Synthesis of Protected KuE on Resin, 4

The Sar-PSMA ligand was synthesised from the KuE motif on the resinunder standard Fmoc solid phase peptide synthesis conditions.

General Fmoc Deprotection Protocol

The resin bound peptide 4 was treated with a solution of 20% piperidinein DMF for 5 min ×3. The resin was then washed consecutively with DMF ×3and DCM ×3.

TNBSA Test for Confirmation of Coupling/Deprotection Reaction

A qualitative test was carried out for each coupling/deprotection stepusing the TNBSA (trinitrobenzenesulfonic acid) test. A small fraction ofthe resin (approx. 20 beads) was placed into an Eppendorf tube. TNBSA(10 μL of 5% solution in DMF) and DIPEA (10 μL of 5% solution in DMF)were added and the mixture was agitated for 2 min. If no color change ofthe resin was observed, the test was indicative of an absence of aprimary amine, whilst an orange color of the resin was indicative of thepresence of a free primary amine.

After deprotection, a solution of the activated Glu intermediate 3 (0.95g, 2.69 mmol, 2.0 eq) and DIPEA (240 μL, 1.38 mmol, 1.0 eq) in DMF (5mL) was added to the resin. The resin was stirred manually over 24 h andwashed with DMF ×3 and DCM ×3. After confirmation of coupling via TNBSAand test cleavage/MS, the DDiv group was deprotected by treatment with2% hydrazine hydrate in DMF ×3 to give 5.

General Protocol for Coupling Fmoc-Amino Acid to Resin

Fmoc amino acid (3 equiv.) was activated using HCTU (0.96 eq relative toAA) and DIPEA (2 eq relative to AA) in DMF. After 5 min, the solutionwas added onto the resin and was occasionally stirred. After 20 min, theresin was filtered and washed consecutively with DMF ×1, DCM ×3, and DMF×3 to give 6.

Coupling of MeCOSar onto PSMA Ligand on Resin to Give 7

BocMeCOSar (0.464 g, 0.5 mmol, 1.2 eq) was activated using HCTU (0.207g), HOBt (67.6 mg), and DIPEA (174 μL) in DMF. After 5 min, the solutionwas added to the resin 6 (0.4 mmol) and occasionally stirred. After 24h, the resin was filtered and washed consecutively with DMF ×1, DCM ×3,and DMF ×3.

Resin Cleavage Protocol to Produce 1

The resin 7 was washed several times with DCM and then transferred to a50 mL falcon tube. 95:2.5:2.5 TFA/TIPS/H₂O (15 mL) was added and theresin was agitated at rt for 2 h. The resin was filtered and washedtwice with 3 mL TFA. The filtrate was collected and the TFA wasevaporated under a stream of N₂. The crude peptide was precipitated byaddition of excess chilled Et₂O and centrifuged. The Et₂O was decantedand the process was repeated ×3. The precipitated crude peptide wasdried and weighed and purified via prep-HPLC.

HPLC Purification

The crude peptide (818 mg) was reconstituted in 22% MeCN in H₂O (6.4 mL)and purified in portions by RP-HPLC (24% isocratic for 60 min) on aKinetex 5p 100 Å AXIA-packed C18 21.2 ×150 mm semi-preparative column at5 mL/min. The fractions containing the product were separated andlyophilized to afford the product 1 as a fluffy white powder (58.5 mg,16.1% based on resin used).

Radiolabeling

An aliquot of ⁶⁴Cu^(II) (30-200 MBq, 0.1M NH₄OAc, pH 6) was added to asolution containing Sar-PSMA 1 (5 μg, 4.3×10⁻³ μmol) in MilliQ water,NH₄OAc, pH 5 (final concentration: 0.05M), ethanol (10%), and gentisicacid in MilliQ water (final concentration: 0.056%) and the pH wasmeasured (pH: 5). The reaction was incubated for 30 min at roomtemperature. After 30 minutes, an aliquot was analysed by RP-HPLC todetermine the product, ⁶⁴Cu-Sar-PSMA with >98% radiochemical purity.

Stability in Plasma

To 200 μL of fresh human plasma at 37° C. was added a solution of⁶⁴Cu-Sar-PSMA in saline (100 uL, ˜8.8 MBq, <10% EtOH) and the mixturewas incubated at 37° C. for 24 hours. After 24 hours, cold acetonitrile(600 μL) was added. The precipitated serum proteins were separated bycentrifugation (13 000 rpm) and 300 μL of the supernatant was removedand concentrated by evaporation. The solution was diluted in water (100μL) and the product analysed by RP-HPLC.

Tumour Imaging in LNCaP Tumor-Bearing Mice

The in vivo biodistribution of ⁶⁴CuSarPSMA was investigated in LNCaPtumor-bearing NSG (NOD SCID Gamma) mice at 1 h, 6 h, and 22 h afterinjection. At 1 h, ⁶⁴CuSarPSMA showed the highest uptake in the kidneysresulting in low tumor/kidney ratios (FIG. 5). However, thebiodistribution data revealed rapid kidney clearance and moderate tumorretention at later timepoints. Despite the moderate retention of⁶⁴Cu-Sar-PSMA in the tumor, there was significant contrast due to rapidclearance from circulation and virtually no background accumulationafter 6 h. Furthermore, low uptake in other PSMA-positive tissues (lung,spleen) allowed high tumor-to-background ratios for ⁶⁴Cu-Sar-PSMA.

Example 2 Synthesis of CoSar(PSMA)₂ Synthesis of Activated GluIntermediate

-   Reference: Duspara, P. A.; Islam, M. S.; Lough, A. 3.; Batey, R. A.,    Synthesis and reactivity of N-alkyl carbamoylimidazoles: development    of N-methyl carbamoylimidazole as a methyl isocyanate equivalent. J    Org Chem 2012, 77 (22), 10362-8.

To a flask containing L-Bis(tbu)Glu HCl (3.56 g, 12.04 mmol, 1.0 eq) andcarbonyl diimidazole (2.15 g, 13.24 mmol, 1.1 eq) was added a 1:5mixture of DMF/MeCN (50 mL). The reaction was stirred overnight at RT.After stirring, the solvent was removed in vacuo and the remaining crudemixture was dissolved and purified via flash chromatography (mobilephase: 7:3:1 petroleum spirits/chloroform/methanol, RF: ˜0.24, 30:1silica/crude mass ratio) to afford the product as a whitesemi-crystalline powder, (2.25 g, 52.9% yield).

Synthesis of Protected Urea

To a flask containing H-Lys(Fmoc)-OtBu.HCl (4.84 g, 10.5 mmol, 1.0 eq)was added activated Glu intermediate (3.71 g, 10.5 mmol, 1.0 eq) andDIPEA (1.83 mL, 10.5 mmol, 1 eq) in DCM (30 mL) and stirred overnight atRT. The reaction mixture was washed with water ×3, brine, and dried overMgSO4 and loaded onto an 80 g Reveleris HP Silica cartridge and purifiedvia Biotage Isolera automatic flash chromatography purification system(mobile phase: 70:30:2.5 petroleum spirits/chloroform/methanol). Thefractions were analysed via TLC (mobile phase: 7:3:1 petroleumspirits/chloroform/methanol, RF: —0.30), combined, and the solvent wasremoved in vacuo to afford the product as a yellow oil, 5.06 g, 68%yield. ESIMS⁺[M+H⁺] m/z 710.386 (experimental), m/z 710.401 (calcd).

Fmoc Cleavage of Urea

To a flask containing the protected urea (5.06 g, 7.13 mmol, 1 eq) wasadded 20% diethylamine in MeCN (100 mL) and the reaction was stirred for7 hours at RT. Aliquots were removed periodically to analyse via MS forcompletion of reaction. After 7 hours, the diethylamine and MeCN werereduced in vacuo to 5 mL, and an additional 50 mL of MeCN was added toazeotrope the diethylamine via rotary evaporator three times. Thereaction mixture was reduced again to 5 mL, 200 mL of 50/50 water/MeCNwas added and the reaction mixture was lyophilized. Due to impuritiesstemming from the incomplete scavenging of the dibenzofulvene moiety,the final product was used without further purification. (Estimated 70%purity) ESIMS⁺[M+H⁺] m/z 488.329 (experimental), m/z 488.333 (calcd).

Synthesis of 8-Aoc-ff Linker on Resin

The 8-Aoc-ff linker was prepared using the following Fmoc protocolbelow.

General Fmoc Deprotection Protocol

The resin bound peptide was treated with a solution of 20% piperidine inDMF for 15 min ×3. The resin was then washed consecutively with DMF ×3and DCM ×3.

Protocol for Loading Fmoc-Aminooctanoic Acid (Fmoc-8-Aoc-OH) to 2-CTResin

Fmoc-8-Aoc-OH (5.00 g, 13.1 mmol, 1.75 eq) and DIPEA (2 eq relative toAA) in 80 mL DCM was added onto 2-CT resin (7.50 g, 1 mmol/g, 1 eq) andstirred. After 2 hr, 8 mL MeOH was added and the resin was stirred anadditional 30 min. The resin was filtered and washed consecutively withDCM ×3, DMF ×3, DCM ×3, MeOH ×2, and Et₂O ×2 and dried. Resin loadingwas calculated using the equation below, and was found to be 0.628mmol/g (6.16 mmol in total)

${{Resin}{Loading}} = {\frac{{{final}{weight}} - {{initial}{weight}}}{MW{of}{Fmoc} - 8 - {Aoc} - {OH}}{mmol}/g}$

Protocol for Coupling Fmoc-D-Phe-OH to Resin

Fmoc-D-Phe-OH (2 eq) was activated using HATU (0.96 eq relative to AA)and DIPEA (2 eq. relative to AA) in NMP. After 5 min, the solution wasadded onto the resin and was stirred for a minimum of 12 hr. The resinwas filtered and washed consecutively with DMF ×1, DCM ×3, and DMF ×3.Then, the coupling was repeated as above for a minimum of 12 hr, beforebeing filtered and washed consecutively with DMF ×1, DCM ×3, and DMF ×3.

Resin Cleavage Protocol

The resin was washed several times with DCM and then transferred to two50 mL falcon tubes. 5% TFA in DCM (75 mL) was added and the resin wasagitated at RT for 2 h. The resin was filtered and washed twice with 15mL 5% TFA in DCM. The filtrate was collected and the solvent was reducedunder a stream of N₂. The crude peptide was redissolved in 50/50water/MeCN and lyophilized to afford the crude peptide. The crudepeptide was used without further purification.

Trifluoroacetamide Protection

To a flask containing the crude peptide linker (1.35 g, 2.98 mmol ifpure, 1 eq) was added ethyl trifluoroacetate (0.532 mL, 4.47 mmol, 1.5eq) and DIPEA (1.04 mL, 5.96 mmol, 2 eq) in MeOH (10 mL). The reactionwas stirred overnight at RT and monitored via MS and analytical HPLC forcomplete conversion of starting material. The MeOH was reduced in vacuoand EtOAc/0.01 M HCl was added to the reaction. The organic layer wasseparated and washed with 0.01 M HCl ×3 and brine, dried over MgSO4 andthe solvent was removed in vacuo and dried to afford the crude product(0.985 g) that was used without further purification. Orbitrap-MS⁺[M+H⁺]m/z 550.253 (experimental), m/z 550.252 (calcd), [2M+H⁺] m/z 1099.498(experimental), m/z 1099.497 (calcd).

Urea-Linker Coupling

To a flask containing the crude TFA-protected linker (0.985 g, 1.79 mmolif pure, 1 eq) was added HATU (0.608 g, 1.6 mmol, 0.89 eq) and DIPEA(0.56 mL, 3.2 mmol, 1.79 eq) in DMF (5 mL) and stirred at RT. After 5minutes, the deprotected urea (approx. 1.5 mmol) was added and thereaction was monitored via MS and analytical HPLC overnight. After 24hr, K₂CO₃ in water was added and the reaction was heated to 60° C.overnight and monitored for removal of the trifluoroacetamide protectinggroup. The reaction was diluted with water (150 mL) and extracted withEt₂O ×3. The ether fractions were combined and washed with water, 0.01 MHCl ×3, and brine, and dried over MgSO4. The aqueous layer was acidifiedwith 0.1 M HCl and extracted with Et₂O, washed with water, 0.01 M HCl,and brine, and dried over MgSO4. The ether layers were combined, thesolvent was removed in vacuo, and the crude product was dissolved in 80%MeCN in water and purified via RP-HPLC (60-77% over 35 min) on aPhenomenex Luna 5p 100 Å C18 21.2×250 mm semi-preparative column at 8mL/min. The fractions containing the product were collected andlyophilized to afford the product as a fluffy white powder (49.6 mg,98%+ purity). Orbitrap-MS⁺[M+H⁺] m/z 923.586 (experimental), m/z 923.585(calcd), [M+2H⁺] m/z 462.297 (experimental), m/z 462.296 (calcd).

Synthesis of (tBoc)₄₋₅CoSar-Plus

(tBoc)₄₋₅CoSar-Plus can be prepared according to procedures in Ma, M.T.; Cooper, M. S.; Paul, R. L.; Shaw, K. P.; Karas, 3. A.; Scanlon, D.;White, 3. M.; Blower, P. 3.; Donnelly, P. S. Inorg Chem 2011, 50, 6701.

Synthesis of CoSar-(PSMA)₂

To an Eppendorf tube was added (tBoc)₄₋₅COSar-Plus (25.3 mg, 0.027 mmol,1 eq), HATU (20.4 mg, 0.054 mmol, 2 eq), and DIPEA (18.7 μL, 0.107 mmol,4 eq.) in NMP (500 μL). The mixture was shaken for 10 minutes to allowfor activation and then added to a 2 mL microwave vial containing thepure PSMA Linker-Urea (49.6 mg, 0.054 mmol, 2 eq) in NMP (400 μL). Thereaction was stirred in the microwave reactor at 60° C. for 10 minutes,cooled, and analysed via MS and analytical HPLC to show completeconsumption of starting material. To the reaction material was added 1.8mL 72% MeCN in water and purified via RP-HPLC (60-90% over 60 min) on aPhenomenex Luna 5μ 100 Å C18 21.2×250 mm semi-preparative column at 8mL/min. The fractions containing the product were collected andlyophilized to afford the protected product as a fluffy white powder(14.0 mg, 5.08 μmol, 18.9% yield). The protected product was dissolvedin 95% TFA in water overnight, diluted with 50/50 MeCN/water, andlyophilized to afford the product as a white powder as thetris-trifluoroacetate monohydrate salt (12.1 mg, 5.08 μmol) (rt: 10.3min, 96.4% purity). Orbitrap-MS⁺[M+2H⁺] m/z 1009.065 (experimental), m/z1009.066 (calcd), [M+3H⁺] m/z 673.046 (experimental), m/z 673.046(calcd).

Radiolabeling

An aliquot of ⁶⁴Cu^(II) (100-400 MBq, 0.01 M HCl) was added to asolution containing 0.1M NH₄OAc, pH 5.5 (500 μL), ethanol (100 μL),MilliQ water (300 μL), and gentisic acid (1.2 mg, 10 mg/mL in MilliQwater) and the pH was measured (pH: 5). To this solution was addedCoSar-(PSMA)₂ (20 μg, 8.4×10⁻³ μmol, 1 mg/mL in MilliQ) and the reactionwas incubated for 30 min at room temperature. After 30 minutes, analiquot was analysed by RP-HPLC to determine the product,⁶⁴Cu-CoSar(PSMA)₂ with >97% radiochemical purity (rt: 13.9 min).

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (orinformation derived from it), or to any matter which is known, is not,and should not be taken as an acknowledgment or admission or any form ofsuggestion that that prior publication (or information derived from it)or known matter forms part of the common general knowledge in the fieldof endeavour to which this specification relates.

1. A compound of Formula (I), or a salt, complex, or solvate thereof:

wherein: X is a group selected from H, OH, halogen, cyano, NO₂, NH₂,optionally substituted C₁-C₁₂ alkyl, optionally substituted amino,optionally substituted amide and optionally substituted aryl; Y is anoptionally substituted C₁-C₁₂ alkylene group, wherein one or more of themethylene groups in the alkylene group may be further optionallysubstituted for a group selected from amide, carbonyl, urea andthiourea; m is 0, 1, or 2; n is 0, 1, or 2; and wherein the compound iscoordinated with ⁶¹Cu.
 2. A compound according to claim 1, or a salt,complex, or solvate thereof, wherein X is an optionally substitutedC₁-C₁₂ alkyl.
 3. A compound according to claim 1, or a salt, complex, orsolvate thereof, wherein X is an optionally substituted amide.
 4. Acompound according to claim 3, or a salt, complex, or solvate thereof,wherein X is the group


5. A compound according to claim 1, or a salt, complex, or solvatethereof, wherein Y is a substituted alkylene group.
 6. A compoundaccording to claim 1, or a salt, complex, or solvate thereof, wherein Yis an alkylene group substituted with an amide group.
 7. A compoundaccording to claim 6, or a salt, complex, or solvate thereof, wherein Yis an alkylene group further substituted with a carbonyl group.
 8. Acompound according to claim 1, or a salt, complex, or solvate thereof,wherein Y is the group


9. A compound according to claim 1, or a salt, complex, or solvatethereof, wherein Y is an unsubstituted alkylene group.
 10. A compoundaccording to claim 9, or a salt, complex, or solvate thereof, wherein Yis a C₁ alkylene group.
 11. A compound according to claim 9, or a salt,complex, or solvate thereof, wherein Y is a methylene group.
 12. Acompound according to claim 1, or a salt, complex, or solvate thereof,wherein m is
 1. 13. A compound according to claim 1, or a salt, complex,or solvate thereof, wherein n is
 1. 14. A compound according to claim 1,or a salt, complex, or solvate thereof, wherein the compound has theformula:


15. A compound or a salt, complex or solvate thereof having thefollowing formula:


16. A compound or a salt, complex or solvate thereof having thefollowing formula:


17. A compound according to claim 1, or a salt, complex, or solvatethereof, wherein the compound has the formula:


18. A compound according to claim 1, or a salt, complex, or solvatethereof, wherein the compound has the formula:


19. A method of treating a condition in a subject in need thereof, themethod comprising administering a therapeutically effective amount of anaqueous composition for parenteral administration comprising a compoundof Formula (I), or a salt, complex, or solvate thereof:

wherein: X is a group selected from H, OH, halogen, cyano, NO₂, NH₂,optionally substituted C₁-C₁₂ alkyl, optionally substituted amino,optionally substituted amide and optionally substituted aryl; Y is anoptionally substituted C₁-C₁₂ alkylene group, wherein one or more of themethylene groups in the alkylene group may be further optionallysubstituted for a group selected from amide, carbonyl, urea andthiourea; m is 0, 1, or 2; and n is 0, 1, or 2; wherein the compound ofFormula (I) is complexed with a metal ion; and wherein the compositionfurther comprises ethanol, gentisic acid or a salt thereof, and sodiumchloride.
 20. The method of claim 19, wherein for the compound ofFormula (I), or the salt, complex, or solvate thereof, X is anoptionally substituted C₁-C₁₂ alkyl.
 21. The method of claim 19, whereinfor the compound of Formula (I), or the salt, complex, or solvatethereof, X is an optionally substituted amide.
 22. The method of claim21, wherein for the compound of Formula (I), or the salt, complex, orsolvate thereof, X is the group


23. The method of claim 19, wherein for the compound of Formula (I), orthe salt, complex, or solvate thereof, Y is a substituted alkylenegroup.
 24. The method of claim 19, wherein for the compound of Formula(I), or the salt, complex, or solvate thereof, Y is an alkylene groupsubstituted with an amide group.
 25. The method of claim 24, wherein forthe compound of Formula (I), or the salt, complex, or solvate thereof, Yis an alkylene group further substituted with a carbonyl group.
 26. Themethod of claim 19, wherein for the compound of Formula (I), or thesalt, complex, or solvate thereof, Y is the group


27. The method of claim 19, wherein for the compound of Formula (I), orthe salt, complex, or solvate thereof, Y is an unsubstituted alkylenegroup.
 28. The method of claim 27, wherein for the compound of Formula(I), or the salt, complex, or solvate thereof, Y is a C₁ alkylene group.29. The method of claim 27, wherein for the compound of Formula (I), orthe salt, complex, or solvate thereof, Y is a methylene group.
 30. Themethod of claim 19, wherein for the compound of Formula (I), or thesalt, complex, or solvate thereof, m is
 1. 31. The method of claim 19,wherein for the compound of Formula (I), or the salt, complex, orsolvate thereof, n is
 1. 32. The method of claim 19, wherein thecompound of Formula (I), or the salt, complex, or solvate thereof, hasthe formula:


33. The method of claim 19, wherein the compound of Formula (I), or thesalt, complex, or solvate thereof, has the formula:


34. The method of claim 19, wherein the compound of Formula (I), or thesalt, complex, or solvate thereof, has the formula:


35. The method of claim 19, wherein the compound of Formula (I), or thesalt, complex, or solvate thereof, has the formula:


36. The method of claim 19, wherein the compound of Formula (I), or thesalt, complex, or solvate thereof, has the formula:


37. The method of claim 1, wherein the compound of Formula (I), or thesalt, complex, or solvate thereof is complexed metal ion selected fromthe group consisting of Cu, Tc, Gd, Ga, In, Co, Re, Fe, Au, Mg, Ca, Ag,Rh, Pt, Bi, Cr, W, Ni, V, Ir, Zn, Cd, Mn, Ru, Pd, Hg, Ti, Lu, Sc and Y.38. The method of claim 19, wherein the metal ion is a radionuclide. 39.The method of claim 19, wherein the metal ion is an ion of copper. 40.The method of claim 19, wherein the metal ion is selected from the groupconsisting of ⁶⁰Cu, ⁶¹Cu, ⁶²Cu, ⁶⁴Cu and ⁶⁷Cu.
 41. The method of claim19, wherein the condition is cancer.
 42. The method of claim 19, whereinthe condition is selected from the group consisting of breast cancer,colon cancer, lung cancer, ovarian cancer, prostate cancer, head and/orneck cancer, renal, gastric, pancreatic cancer, brain cancer, ahematologic malignancy, lymphoma and leukaemia.
 43. A method of claim19, wherein the condition is prostate cancer.
 44. A method ofradioimaging a subject, the method comprising administering an effectiveamount of an aqueous composition for parenteral administrationcomprising a compound of Formula (I), or a salt, complex, or solvatethereof:

wherein: X is a group selected from H, OH, halogen, cyano, NO₂, NH₂,optionally substituted C₁-C₁₂ alkyl, optionally substituted amino,optionally substituted amide and optionally substituted aryl; Y is anoptionally substituted C₁-C₁₂ alkylene group, wherein one or more of themethylene groups in the alkylene group may be further optionallysubstituted for a group selected from amide, carbonyl, urea andthiourea; m is 0, 1, or 2; and n is 0, 1, or 2; wherein the compound ofFormula (I) is complexed with a metal ion; and wherein the compositionfurther comprises ethanol, gentisic acid or a salt thereof, and sodiumchloride.